DOI： 10.5194/egusphere-2023-197-supplement

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

Visualization of dust flow and wind dynamics near the ground surface are essential for understanding the mixing and interaction between geosphere and atmosphere near the surface. Knowing the temporal dust flow is beneficial in dealing with air pollution and health issues. Dust flows near the ground surface are difficult to monitor because of their small temporal and spatial scale. In this study, we propose a low-coherence Doppler lidar (LCDL) for measuring dust flow near the ground with high temporal and spatial resolutions of 5 ms and 1 m, respectively. We demonstrate the performance of LCDL in laboratory experiments using flour and calcium carbonate particles released into the wind tunnel. LCDL experiment results show a good agreement with anemometer measurement in wind speeds ranging from 0 to 5 m/s. The LCDL technique can reveal dust’s speed distribution, which is affected by mass and particle size. As a result, different speed distribution profiles can be used to determine dust type. The simulation results of dust flow coincide well with the experimental results.

DOI： 10.1038/s41598-023-30346-z

Web of Science

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Other Link： https://www.nature.com/articles/s41598-023-30346-z

Language：English   Publishing type：Research paper (scientific journal)  

An optical coherence tomography (OCT) system based on the ghost imaging (GI) technique is developed for correctly imaging in scattering media. Usually, the scattering in the media leads to a decrease in the signal-to-noise ratio of the reconstructed image. This problem can be solved by using ghost imaging-OCT(GI-OCT), but the number of patterns required for GI reconstruction depends on the concentration of the scattering media. Therefore, studying the relationship between the intensity distribution in reconstructed images and the optical properties of scattering media is essential. In this study, image reconstruction is carried out in scattering media with a concentration of 0.0% to 1.4%, diluted from processed milk. Using the structural similarity index method (SSIM) to analyze the reconstruction condition, it is found that the target image can be reconstructed correctly when the SSIM value is more than 0.7. By analyzing the intensity distribution of the reconstructed image, the results show that the extinction coefficient of the scattering media is negatively correlated with the contrast of the reconstructed image and positively correlated with the scattering intensity. Their correlation coefficients are -0.94 and 0.99, respectively.

DOI： https://doi.org/10.3390/photonics10020146

Publishing type：Research paper (international conference proceedings)   Publisher：SCITEPRESS  

DOI： 10.5220/0011677400003408

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Other Link： https://dblp.uni-trier.de/db/conf/photoptics/photoptics2023.html#HuyanLS23

Language：English   Publishing type：Research paper (scientific journal)   Publisher：{AIP} Publishing  

When the conventional optical coherence tomography (OCT) measures the transmittance and the absorbance of the target in the scattering media, its image is affected by the scattering media and gets a modulated target profile. Due to the influence of scattering and absorption by the media, the conventional OCT cannot eliminate this modulation. By using our proposed idea, ghost imaging-OCT (GI-OCT), to apply the GI technique to the measurement path of OCT, we can reconstruct the target profile in the scattering media without modulation. In this work, we introduce and demonstrate the concept and the experimental method of GI-OCT. This application can correct the influence of the scattering media for the target optical profile due to the advantage of the GI technique, which suppresses noise, here, modulated by scattering. Comparing the experimental results of the corrected target image with the original target image, we obtain the same distributions in the binarized images, and the error of the character size in the binarized deconvoluted image is less than the resolution of the image (0.04 mm), proving that the method successfully reconstructs the image without the scattering media influence.

DOI： 10.1063/5.0099638

Web of Science

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Language：English   Publishing type：Research paper (scientific journal)  

The propagation methods of a non-diffractive beam (NDB) for optical sensing in scattering media have been extensively studied. However, those methods can realize the high resolution and long depth of focus in the viewpoint of microscopic imaging. In this study, we focus on macroscopic sensing in living tissues with a depth of a few tens centimeters. An experimental approach for generating adequate NDB in dense scattering media based on the linear relationship between propagation distance and transport mean free path is reported. For annular beams with different diameters, the same changes of the center intensity ratio of NDB are obtained from the experiment results. They are discussed with theoretical analysis. As a result, the maximum center intensity ratio of the adequate generated NDB can be estimated at arbitrary propagation distance in the dense scattering media.

DOI： https://doi.org/10.1038/s41598-022-12810-4

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI  

Comparing cloud cover (CC) products from different satellites with the same ground-based CC dataset provides information on the similarities or differences of values among satellite products. For this reason, 42-month CC products from Moderate Resolution Imaging Spectrometer's (MODIS) Collection 6.1 daily cloud cover products (MOD06_L2, MYD06_L2, MOD08_D3, and MYD08_D3) and Himawari-8 are compared with the ground-based camera datasets. The comparison shows that CC from MODIS differs from ground measurement CC by as much as 57% over Chiba, Japan, when low CC is observed by the camera. This indicates MODIS's ability to capture high-level clouds that are not effectively seen from the ground. When the camera detects high CC, an indication of the presence of low-level clouds, CC from MODIS is relatively higher than the CC from the camera. In the case of Himawari-8 data, when the camera observes low CC, this difference is around 0.7%. This result indicates that high-level clouds are not effectively observed, but the Himawari-8 data correlates well with camera observations. When the camera observes high CC, Himawari-8-derived CC is lower by around 10% than CC from the camera. These results show the potential of continuous observations of nighttime clouds using the camera to provide a dataset that can be used for intercomparison among nighttime satellite CC products.

DOI： 10.3390/rs14040960

Web of Science

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Language：English   Publishing type：Research paper (scientific journal)  

Comparing cloud cover (CC) products from different satellites with the same ground-based CC dataset provides information on the similarities or differences of values among satellite products. For this reason, 42-month CC products from Moderate Resolution Imaging Spectrometer’s (MODIS) Collection 6.1 daily cloud cover products (MOD06_L2, MYD06_L2, MOD08_D3, and MYD08_D3) and Himawari-8 are compared with the ground-based camera datasets. The comparison shows that CC from MODIS differs from ground measurement CC by as much as 57% over Chiba, Japan, when low CC is observed by the camera. This indicates MODIS’s ability to capture high-level clouds that are not effectively seen from the ground. When the camera detects high CC, an indication of the presence of low-level clouds, CC from MODIS is relatively higher than the CC from the camera. In the case of Himawari-8 data, when the camera observes low CC, this difference is around 0.7%. This result indicates that high-level clouds are not effectively observed, but the Himawari-8 data correlates well with camera observations. When the camera observes high CC, Himawari-8-derived CC is lower by around 10% than CC from the camera. These results show the potential of continuous observations of nighttime clouds using the camera to provide a dataset that can be used for intercomparison among nighttime satellite CC products.

DOI： https://doi.org/10.3390/rs14040960

Language：English   Publishing type：Research paper (scientific journal)  

Comparing cloud cover (CC) products from different satellites with the same ground-based CC dataset provides information on the similarities or differences of values among satellite products. For this reason, 42-month CC products from Moderate Resolution Imaging Spectrometer’s (MODIS) Collection 6.1 daily cloud cover products (MOD06_L2, MYD06_L2, MOD08_D3, and MYD08_D3) and Himawari-8 are compared with the ground-based camera datasets. The comparison shows that CC from MODIS differs from ground measurement CC by as much as 57% over Chiba, Japan, when low CC is observed by the camera. This indicates MODIS’s ability to capture high-level clouds that are not effectively seen from the ground. When the camera detects high CC, an indication of the presence of low-level clouds, CC from MODIS is relatively higher than the CC from the camera. In the case of Himawari-8 data, when the camera observes low CC, this difference is around 0.7%. This result indicates that high-level clouds are not effectively observed, but the Himawari-8 data correlates well with camera observations. When the camera observes high CC, Himawari-8-derived CC is lower by around 10% than CC from the camera. These results show the potential of continuous observations of nighttime clouds using the camera to provide a dataset that can be used for intercomparison among nighttime satellite CC products.

DOI： https://doi.org/10.1029/2021JD034772

Language：English   Publishing type：Research paper (scientific journal)  

Globally consistent measurements of airborne metal concentrations in fine particulate matter (PM2.5) are important for understanding potential health impacts, prioritizing air pollution mitigation strategies, and enabling global chemical transport model development. PM2.5 filter samples (N ~ 800 from 19 locations) collected from a globally distributed surface particulate matter sampling network (SPARTAN) between January 2013 and April 2019 were analyzed for particulate mass and trace metals content. Metal concentrations exhibited pronounced spatial variation, primarily driven by anthropogenic activities. PM2.5 levels of lead, arsenic, chromium, and zinc were significantly enriched at some locations by factors of 100–3000 compared to crustal concentrations. Levels of metals in PM2.5 and PM10 exceeded health guidelines at multiple sites. For example, Dhaka and Kanpur sites exceeded the US National Ambient Air 3-month Quality Standard for lead (150 ng m−3). Kanpur, Hanoi, Beijing and Dhaka sites had annual mean arsenic concentrations that approached or exceeded the World Health Organization’s risk level for arsenic (6.6 ng m−3). The high concentrations of several potentially harmful metals in densely populated cites worldwide motivates expanded measurements and analyses.

DOI： https://doi.org/10.1038/s41598-020-78789-y

Language：English   Publishing type：Research paper (scientific journal)  

Aerosol optical properties are measured near the surface level using sampling instruments and a near-horizontal lidar. The values of the aerosol extinction coefficient inside the instruments are derived from nephelometer and aethalometer data, while the ambient values are measured from the lidar. The information on aerosol size distribution from optical particle counters is used to simulate extinction coefficients using the Mie scattering theory, with corrections on the humidity growth of hygroscopic particles. By applying this method to the continuous data obtained from November to December 2018 at Chiba, Japan, we elucidate the temporal variations of near-surface aerosol properties, including the complex refractive index, single scattering albedo, and Angstrom exponent. The results indicate how aerosol particles change their properties between the dry, instrumental conditions and relatively humid setting of the ambient atmosphere.

DOI： https://doi.org/10.1364/AO.398673

Language：English   Publishing type：Research paper (scientific journal)  

The South China Sea (SCS) is a receptor of numerous natural and anthropogenic aerosol species from throughout greater Asia. A combination of several developing countries, archipelagic and peninsular terrain, a strong Asian monsoon climate, and a host of multi-scale meteorological phenomena make the SCS one of the most complex aerosol–meteorological systems in the world. However, aside from the well-known biomass burning emissions from Indonesia and Borneo, the current understanding of aerosol sources is limited, especially in remote marine environments. In September 2011, a 2-week research cruise was conducted near Palawan, Philippines, to sample the remote SCS environment. Size-segregated aerosol data were collected using a Davis Rotating Uniform size-cut Monitor (DRUM) sampler and analyzed for concentrations of 28 elements measured via X-ray fluorescence (XRF). Positive matrix factorization (PMF) was performed separately on the coarse, fine, and ultrafine size ranges to determine possible sources and their contributions to the total elemental particulate matter mass. The PMF analysis resolved six sources across the three size ranges: biomass burning, oil combustion, soil dust, a crustal–marine mixed source, sea spray, and fly ash. Additionally, size distribution plots, time series plots, back trajectories and satellite data were used in interpreting factors. The multi-technique source apportionment revealed the presence of biogenic sources such as soil dust, sea spray, and a crustal–marine mixed source. Anthropogenic sources were also identified: biomass burning, oil combustion, and fly ash. Mass size distributions showed elevated aerosol concentrations towards the end of the sampling period, which coincided with a shift of air mass back trajectories to southern Kalimantan. Covariance between coarse-mode soil dust and fine-mode biomass burning aerosols were observed. Agreement between the PMF and the linear regression analyses indicates that the PMF solution is robust. While biomass burning is indeed a key source of aerosol, this study shows the presence of other important sources in the SCS. Identifying these sources is not only key for characterizing the chemical profile of the SCS but, by improving our picture of aerosol sources in the region, also a step forward in developing our understanding of aerosol–meteorology feedbacks in this complex environment.

DOI： https://doi.org/10.5194/acp-20-1255-2020

Language：English   Publishing type：Research paper (scientific journal)  

Studying near-surface aerosol properties is of importance for a better assessment of the aerosol effect on radiative forcing. We employ the data from a near-horizontal lidar to investigate the diurnal behavior of aerosol extinction and single scattering albedo (SSA) at 349 nm. The response of these parameters to ambient relative humidity (RH) is examined for the data from a one-month campaign conducted in Chiba, Japan, during November 2017, a transition period from fall to winter. The Klett method and adaptive slope method are used in deriving the aerosol extinction coefficient from the lidar data, while the SSA values are retrieved using an aethalometer. Also, a visibility-meter is used to examine the aerosol loading inside the atmospheric boundary layer. It is found that the aerosol growth during the deliquescence phase is more readily observed than the contraction in the efflorescence phase. The decrease of SSA before the deliquescence RH is found for approximately 46% of the deliquescence cases, presumably representing the particle shrinkage of soot particles.

DOI： https://doi.org/10.3390/atmos11010036

Language：English   Publishing type：Research paper (scientific journal)  

Cloud classification is not only important for weather forecasts, but also for radiation budget studies. Although cloud mask and classification procedures have been proposed for Himawari-8 Advanced Himawari Imager (AHI), their applicability is still limited to daytime imagery. The split window algorithm (SWA), which is a mature algorithm that has long been exploited in the cloud analysis of satellite images, is based on the scatter diagram between the brightness temperature (BT) and BT difference (BTD). The purpose of this research is to examine the usefulness of the SWA for the cloud classification of both daytime and nighttime images from AHI. We apply SWA also to the image data from Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Aqua and Terra to highlight the capability of AHI. We implement the cloud analysis around Japan by employing band 3 (0.469 μm) of MODIS and band 1 (0.47 μm) of AHI for extracting the cloud-covered regions in daytime. In the nighttime case, the bands that are centered at 3.9, 11, 12, and 13 µm are utilized for both MODIS and Himawari-8, with somewhat different combinations for land and sea areas. Thus, different thresholds are used for analyzing summer and winter images. Optimum values for BT and BTD thresholds are determined for the band pairs of band 31 (11.03 µm) and 32 (12.02 µm) of MODIS (SWA31-32) and band 13 (10.4 µm) and 15 (12.4 µm) of AHI (SWA13-15) in the implementation of SWA. The resulting cloud mask and classification are verified while using MODIS standard product (MYD35) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data. It is found that MODIS and AHI results both capture the essential characteristics of clouds reasonably well in spite of the relatively simple scheme of SWA based on four threshold values, although a broader spread of BTD obtained with Himawari-8 AHI (SWA13-15) could possibly lead to more consistent results for cloud-type classification than SWA31-32 based on the MODIS sensors.

DOI： https://doi.org/10.3390/rs11242944

Language：English   Publishing type：Research paper (scientific journal)  

In this study, we used ground instruments, namely, a visibility meter, an integrating nephelometer, an aethalometer, a lidar, and a weather monitor, to measure the scattering enhancement factor, f(RH), which quantifies the effect of ambient relative humidity (RH) on aerosol light-scattering, and to generate a model of its annual variation in the city of Chiba, Japan. First, the f(RH) values were calculated with chemical analysis data. Second, visibility-meter and aethalometer data were used to model the monthly trends of f(RH) at 550 nm. The f(RH) values were higher during summer than during the other three seasons, which can be attributed to the general pattern of the regional climatology as well as the loading of different particle types into the lower troposphere. Third, the f(RH) values at 532 nm were obtained from lidar and aethalometer measurements. Low and constant f(RH) values were observed during November, whereas higher and increasing f(RH) values were observed during May. Also, dust events during March 2015 showed decreasing f(RH) with increasing RH .

DOI： https://doi.org/10.4209/aaqr.2018.07.0267

Language：English   Publishing type：Research paper (scientific journal)  

Exposure to ambient fine particulate matter (PM2.5) is a leading risk factor for the global burden of disease. However, uncertainty remains about PM2.5 sources. We use a global chemical transport model (GEOS-Chem) simulation for 2014, constrained by satellite-based estimates of PM2.5 to interpret globally dispersed PM2.5 mass and composition measurements from the ground-based surface particulate matter network (SPARTAN). Measured site mean PM2.5 composition varies substantially for secondary inorganic aerosols (2.4–19.7 μg/m³), mineral dust (1.9–14.7 μg/m³), residual/organic matter (2.1–40.2 μg/m³), and black carbon (1.0–7.3 μg/m³). Interpretation of these measurements with the GEOS-Chem model yields insight into sources affecting each site. Globally, combustion sectors such as residential energy use (7.9 μg/m³), industry (6.5 μg/m³), and power generation (5.6 μg/m³) are leading sources of outdoor global population-weighted PM2.5 concentrations. Global population-weighted organic mass is driven by the residential energy sector (64%) whereas population-weighted secondary inorganic concentrations arise primarily from industry (33%) and power generation (32%). Simulation-measurement biases for ammonium nitrate and dust identify uncertainty in agricultural and crustal sources. Interpretation of initial PM2.5 mass and composition measurements from SPARTAN with the GEOS-Chem model constrained by satellite-based PM2.5 provides insight into sources and processes that influence the global spatial variation in PM2.5 composition.

DOI： https://doi.org/10.1021/acs.est.8b01658

Language：English   Publishing type：Research paper (scientific journal)  

Observation of optical properties of atmospheric aerosols, especially their behavior near the surface level, is indispensable for better understanding of atmospheric environmental conditions. Concurrent observations of ground-based instruments and satellite-borne sensors are useful for attaining improved accuracy in the observation of relatively wide area. In the present paper, aerosol parameters in the lower troposphere are monitored using a plan position indicator (PPI) lidar, ground-sampling instruments (a nephelometer, an aethalometer, and optical particle counters), as well as a sunphotometer. The purpose of these observations is to retrieve the aerosol extinction coefficient (AEC) and aerosol optical thickness (AOT) simultaneously at the overpass time of Landsat-8 satellite. The PPI lidar, operated at 349 nm, provides nearly horizontal distribution of AEC in the lower part of the atmospheric boundary layer. For solving the lidar equation, the boundary condition and lidar ratio are determined from the data of ground sampling instruments. The value of AOT, on the other hand, is derived from sunphotometer, and used to analyze the visible band imagery of Landsat-8 satellite. The radiative transfer calculation is conducted using the MODTRAN code with the original aerosol type that has been determined from the ground sampling data coupled with the Mie scattering calculation. Reasonable agreement is found between the spatial distribution of AEC from the PPI lidar and that of AOT from the blue band (band 2) of Landsat-8. The influence of AOT on the values of apparent surface reflectance is also discussed.

DOI： https://doi.org/10.4236/ars.2018.73013

Language：English   Publishing type：Research paper (scientific journal)  

Cloud detection and classification form a basis in weather analysis. Split window algorithm (SWA) is one of the simple and matured algorithms used to detect and classify water and ice clouds in the atmosphere using satellite data. The recent availability of Himawari-8 data has considerably strengthened the possibility of better cloud classification owing to its enhanced multi-band configuration as well as high temporal resolution. In SWA, cloud classification is attained by considering the spatial distributions of the brightness temperature (BT) and brightness temperature difference (BTD) of thermal infrared bands. In this study, we compare unsupervised classification results of SWA using the band pair of band 13 and 15 (SWA13-15, 10 and 12 μm bands), versus that of band 15 and 16 (SWA15-16, 12 and 13 μm bands) over the Japan area. Different threshold values of BT and BTD are chosen in winter and summer seasons to categorize cloud regions into nine different types. The accuracy of classification is verified by using the cloud-top height information derived from the data of Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). For this purpose, six different paths of the space-borne lidar are selected in both summer and winter seasons, on the condition that the time span of overpass falls within the time ranges between 01:00 and 05:00 UTC, which corresponds to the local time around noon. The result of verification indicates that the classification based on SWA13-15 can detect more cloud types as compared with that based on SWA15-16 in both summer and winter seasons, though the latter combination is useful for delineating cumulonimbus underneath dense cirrus regions.

DOI： https://doi.org/10.4236/ars.2018.73015

Language：English   Publishing type：Research paper (scientific journal)  

Night-time cloud detection provides data sets of cloud-cover percentage. Although night-time cloud-cover data sets from satellite-based instruments are common, these data sets do not have relatively high temporal resolution. To quantify local temporal cloud-cover variability and to attain long-term cloud-cover measurements, ground-based instruments would be the appropriate apparatus. In this study, a digital camera is used to continuously gather images of the night sky at 5-min intervals over Manila Observatory (14.64° N, 121.07° E). For the first time in Manila, ground-based remote-sensing data gathered from October 2015 to October 2016 are analysed for hourly cloud cover. The results indicate that wet season has relatively higher cloud-cover values (median >40%) as compared to the dry season (median <40%). Moreover, cloud-cover values are observed to decrease during the night. For the wet season, August having the highest cloud-cover values has the highest value of change of hourly cloud-cover percentage (−0.82% h#U−1#U). For the dry season, February having the lowest cloud-cover values has the highest value of change of hourly cloud-cover percentage (−1.04% h#U−1#U).

DOI： https://doi.org/10.1080/01431161.2018.1475776

Language：English   Publishing type：Research paper (scientific journal)  

The understanding of aerosol properties in troposphere, especially their behavior near the ground level, is indispensable for precise evaluation of their impact on the Earth’s radiation studies. Although a sunphotometer or a skyradiometer can provide the aerosol optical thickness (AOT), their application is limited to daytime under near cloud free conditions. In order to attain the multi-wavelength observation for both day- and night-time including cloudy conditions, here we propose a novel monitoring technique by means of simultaneous measurement using a nephelometer (450, 550, and 700 nm), an aethalometer (370, 470, 520, 590, 660, 880, and 950 nm), and a visibility meter (550 nm). On the basis of the multi-wavelength data of scattering and absorption coefficients from the nephelometer and aethalometer, respectively, first we calculate the real-time values of aerosol extinction coefficient in addition to the Angstrom exponent (AE). Then, correction of these values is carried out by comparing the resulting extinction coefficient with the corresponding value obtained from the optical data of visibility-meter. The major reason for this correction is the loss of relatively coarse particles due to the aerodynamic effect as well as evaporation of water content from particles during the sampling procedure. Then, with the ancillary data of vertical aerosol profile obtained with a lidar (532 nm), the temporal change of AOT is estimated. In this
way, information from the sampling can be converted to the ambient properties in the atmospheric boundary layer. Furthermore, daytime data from a sunphotometer (368, 500, 675, and 778 nm) and a skyradiometer (340, 380, 400, 500, 675, 870, and 1020 nm) are used to validate the resulting AOT values. From the overall procedure, we can estimate the AE and AOT values from the sampling data, with uncertainties of approximately 5% for AE and 10% for AOT. Such a capability will be useful for studying aerosol properties throughout 24 hours regardless of the solar radiation and cloud coverage.

DOI： https://doi.org/10.4236/ojap.2018.72008

Language：English   Publishing type：Research paper (scientific journal)  

Ship-based measurements of aerosol and cloud condensation nuclei (CCN) properties are presented for 2 weeks of observations in remote marine regions of the South China Sea/East Sea during the southwestern monsoon (SWM) season. Smoke from extensive biomass burning throughout the Maritime Continent advected into this region during the SWM, where it was mixed with anthropogenic continental pollution and emissions from heavy shipping activities. Eight aerosol types were identified using a k-means cluster analysis with data from a size-resolved CCN characterization system. Interpretation of the clusters was supplemented by additional onboard aerosol and meteorological measurements, satellite, and model products for the region. A typical bimodal marine boundary layer background aerosol population was identified and observed mixing with accumulation mode aerosol from other sources, primarily smoke from fires in Borneo and Sumatra. Hygroscopicity was assessed using the κ parameter and was found to average 0.40 for samples dominated by aged accumulation mode smoke; 0.65 for accumulation mode marine aerosol; 0.60 in an anthropogenic aerosol plume; and 0.22 during a short period that was characterized by elevated levels of volatile organic compounds not associated with biomass burning impacts. As a special subset of the background marine aerosol, clean air masses substantially scrubbed of particles were observed following heavy precipitation or the passage of squall lines, with changes in observed aerosol properties occurring on the order of minutes. Average CN number concentrations, size distributions, and κ values are reported for each population type, along with CCN number concentrations for particles that activated at supersaturations between 0.14 and 0.85 %.

DOI： https://doi.org/10.5194/acp-17-1105-2017

Language：English   Publishing type：Research paper (scientific journal)  

The largest 7 Southeast Asian Studies (7SEAS) operation period within the Maritime Continent (MC) occurred in the August–September 2012 biomass burning season. Included was an enhanced deployment of Aerosol Robotic Network (AERONET) sun photometers, multiple lidars, and field measurements to observe transported smoke and pollution as it left the MC and entered the southwest monsoon trough. Here we describe the nature of the overall 2012 southwest monsoon (SWM) and biomass burning season to give context to the 2012 deployment. The MC in 2012 was in a slightly warm El Niño/Southern Oscillation (ENSO) phase and with spatially typical burning activity. However, overall fire counts for 2012 were 10 % lower than the Reid et al. (2012) baseline, with regions of significant departures from this norm, ranging from southern Sumatra (+30 %) to southern Kalimantan (−42 %). Fire activity and monsoonal flows for the dominant burning regions were modulated by a series of intraseasonal oscillation events (e.g., Madden–Julian Oscillation, or MJO, and boreal summer intraseasonal oscillation, or BSISO). As is typical, fire activity systematically progressed eastward over time, starting with central Sumatran fire activity in June related to a moderately strong MJO event which brought drier air from the Indian Ocean aloft and enhanced monsoonal flow. Further burning in Sumatra and Kalimantan Borneo occurred in a series of significant events from early August to a peak in the first week of October, ending when the monsoon started to migrate back to its wintertime northeastern flow conditions in mid-October. Significant monsoonal enhancements and flow reversals collinear with tropical cyclone (TC) activity and easterly waves were also observed. Islands of the eastern MC, including Sulawesi, Java, and Timor, showed less sensitivity to monsoonal variation, with slowly increasing fire activity that also peaked in early October but lingered into November. Interestingly, even though fire counts were middling, resultant AERONET 500 nm aerosol optical thickness (AOT) from fire activity was high, with maximums of 3.6 and 5.6 in the Sumatra and Kalimantan source regions at the end of the burning season and an average of ∼ 1. AOTs could also be high at receptor sites, with a mean and maximum of 0.57 and 1.24 in Singapore and 0.61 and 0.8 in Kuching Sarawak. Ultimately, outside of the extreme 2015 El Niño event, average AERONET AOT values were higher than any other time since sites were established. Thus, while satellite fire data, models, and AERONET all qualitatively agree on the nature of smoke production and transport, the MC's complex environment resulted in clear differences in quantitative interpretation of these datasets.

DOI： https://doi.org/10.5194/acp-16-14041-2016

Language：English   Publishing type：Research paper (scientific journal)  

The Surface PARTiculate mAtter Network (SPARTAN) is a long-term project that includes characterization of chemical and physical attributes of aerosols from filter samples collected worldwide. This paper discusses the ongoing efforts of SPARTAN to define and quantify major ions and trace metals found in fine particulate matter (PM2.5). Our methods infer the spatial and temporal variability of PM2.5 in a cost-effective manner. Gravimetrically weighed filters represent multi-day averages of PM2.5, with a collocated nephelometer sampling air continuously. SPARTAN instruments are paired with AErosol RObotic NETwork (AERONET) sun photometers to better understand the relationship between ground-level PM2.5 and columnar aerosol optical depth (AOD).

We have examined the chemical composition of PM2.5 at 12 globally dispersed, densely populated urban locations and a site at Mammoth Cave (US) National Park used as a background comparison. So far, each SPARTAN location has been active between the years 2013 and 2016 over periods of 2–26 months, with an average period of 12 months per site. These sites have collectively gathered over 10 years of quality aerosol data. The major PM2.5 constituents across all sites (relative contribution ± SD) are ammoniated sulfate (20 % ± 11 %), crustal material (13.4 % ± 9.9 %), equivalent black carbon (11.9 % ± 8.4 %), ammonium nitrate (4.7 % ± 3.0 %), sea salt (2.3 % ± 1.6 %), trace element oxides (1.0 % ± 1.1 %), water (7.2 % ± 3.3 %) at 35 % RH, and residual matter (40 % ± 24 %).

Analysis of filter samples reveals that several PM2.5 chemical components varied by more than an order of magnitude between sites. Ammoniated sulfate ranges from 1.1 µg m−3 (Buenos Aires, Argentina) to 17 µg m−3 (Kanpur, India in the dry season). Ammonium nitrate ranged from 0.2 µg m−3 (Mammoth Cave, in summer) to 6.8  µg m−3 (Kanpur, dry season). Equivalent black carbon ranged from 0.7 µg m−3 (Mammoth Cave) to over 8 µg m−3 (Dhaka, Bangladesh and Kanpur, India). Comparison of SPARTAN vs. coincident measurements from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network at Mammoth Cave yielded a high degree of consistency for daily PM2.5 (r2 = 0.76, slope  =  1.12), daily sulfate (r2 = 0.86, slope  =  1.03), and mean fractions of all major PM2.5 components (within 6 %). Major ions generally agree well with previous studies at the same urban locations (e.g. sulfate fractions agree within 4 % for 8 out of 11 collocation comparisons). Enhanced anthropogenic dust fractions in large urban areas (e.g. Singapore, Kanpur, Hanoi, and Dhaka) are apparent from high Zn : Al ratios.

The expected water contribution to aerosols is calculated via the hygroscopicity parameter κv for each filter. Mean aggregate values ranged from 0.15 (Ilorin) to 0.28 (Rehovot). The all-site parameter mean is 0.20 ± 0.04. Chemical composition and water retention in each filter measurement allows inference of hourly PM2.5 at 35 % relative humidity by merging with nephelometer measurements. These hourly PM2.5 estimates compare favourably with a beta attenuation monitor (MetOne) at the nearby US embassy in Beijing, with a coefficient of variation r2 =  0.67 (n =  3167), compared to r2 = 0.62 when κv was not considered. SPARTAN continues to provide an open-access database of PM2.5 compositional filter information and hourly mass collected from a global federation of instruments.

DOI： https://doi.org/10.5194/acp-16-9629-2016, 2016

Language：English   Publishing type：Research paper (scientific journal)  

Ground-based cloud detection at nighttime is achieved by using cameras, lidars, and ceilometers. Despite these numerous instruments gathering cloud data, there is still an acknowledged scarcity of information on quantified local cloud cover, especially at nighttime. In this study, a digital camera is used to continuously collect images near the sky zenith at nighttime in an urban environment. An algorithm is developed to analyze pixel values of images of nighttime clouds. A minimum threshold pixel value of 17 is assigned to determine cloud occurrence. The algorithm uses temporal averaging to estimate the cloud fraction based on the results within the limited field of view. The analysis of the data from the months of January, February, and March 2015 shows that cloud occurrence is low during the months with relatively lower minimum temperature (January and February), while cloud occurrence during the warmer month (March) increases.

DOI： https://doi.org/10.1364/AO.55.006040

Language：English   Publishing type：Research paper (scientific journal)  

The largest 7 Southeast Asian Studies (7SEAS) operations period within the Maritime Continent (MC) occurred in the August–September 2012 biomass burning season. Data included were observations aboard the M/Y Vasco, dispatched to the Palawan Archipelago and Sulu Sea of the Philippines for September 2012. At these locations, the Vasco observed MC smoke and pollution entering the southwest monsoon (SWM) monsoonal trough. Here we describe the research cruise findings and the finer-scale aerosol meteorology of this convectively active region. This 2012 cruise complemented a 2-week cruise in 2011 and was generally consistent with previous findings in terms of how smoke emission and transport related to monsoonal flows, tropical cyclones (TC), and the covariance between smoke transport events and the atmosphere's thermodynamic structure. Biomass burning plumes were usually mixed with significant amounts of anthropogenic pollution. Also key to aerosol behavior were squall lines and cold pools propagating across the South China Sea (SCS) and scavenging aerosol particles in their path. However, the 2012 cruise showed much higher modulation in aerosol frequency than its 2011 counterpart. Whereas in 2011 large synoptic-scale aerosol events transported high concentrations of smoke into the Philippines over days, in 2012 measured aerosol events exhibited a much shorter-term variation, sometimes only 3–12 h. Strong monsoonal flow reversals were also experienced in 2012. Nucleation events in cleaner and polluted conditions, as well as in urban plumes, were observed. Perhaps most interestingly, several cases of squall lines preceding major aerosol events were observed, as opposed to 2011 observations where these lines largely scavenged aerosol particles from the marine boundary layer. Combined, these observations indicate pockets of high and low particle counts that are not uncommon in the region. These perturbations are difficult to observe by satellite and very difficult to model. Indeed, the Navy Aerosol Analysis and Prediction System (NAAPS) simulations captured longer period aerosol events quite well but largely failed to capture the timing of high-frequency phenomena. Ultimately, the research findings of these cruises demonstrate the real world challenges of satellite-based missions, significant aerosol life cycle questions such as those the future Aerosol/Clouds/Ecosystems (ACE) will investigate, and the importance of small-scale phenomena such as sea breezes, squall lines, and nucleation events embedded within SWM patterns in dominating aerosol life cycle and potential relationships to clouds.

DOI： https://doi.org/10.5194/acp-16-14057-2016

Language：English   Publishing type：Research paper (scientific journal)  

In a joint NRL/Manila Observatory mission, as part of the Seven SouthEast Asian Studies program (7-SEAS), a 2-week, late September 2011 research cruise in the northern Palawan archipelago was undertaken to observe the nature of southwest monsoonal aerosol particles in the South China Sea/East Sea (SCS/ES) and Sulu Sea region. Previous analyses suggested this region as a receptor for biomass burning from Borneo and Sumatra for boundary layer air entering the monsoonal trough. Anthropogenic pollution and biofuel emissions are also ubiquitous, as is heavy shipping traffic. Here, we provide an overview of the regional environment during the cruise, a time series of key aerosol and meteorological parameters, and their interrelationships. Overall, this cruise provides a narrative of the processes that control regional aerosol loadings and their possible feedbacks with clouds and precipitation. While 2011 was a moderate El Niño–Southern Oscillation (ENSO) La Niña year, higher burning activity and lower precipitation was more typical of neutral conditions. The large-scale aerosol environment was modulated by the Madden–Julian Oscillation (MJO) and its associated tropical cyclone (TC) activity in a manner consistent with the conceptual analysis performed by Reid et al. (2012). Advancement of the MJO from phase 3 to 6 with accompanying cyclogenesis during the cruise period strengthened flow patterns in the SCS/ES that modulated aerosol life cycle. TC inflow arms of significant convection sometimes span from Sumatra to Luzon, resulting in very low particle concentrations (minimum condensation nuclei CN < 150 cm−3, non-sea-salt PM2.5 < 1 μg m−3). However, elevated carbon monoxide levels were occasionally observed suggesting passage of polluted air masses whose aerosol particles had been rained out. Conversely, two drier periods occurred with higher aerosol particle concentrations originating from Borneo and Southern Sumatra (CN > 3000 cm−3 and non-sea-salt PM2.5 10–25 μg m−3). These cases corresponded with two different mechanisms of convection suppression: lower free-tropospheric dry-air intrusion from the Indian Ocean, and large-scale TC-induced subsidence. Veering vertical wind shear also resulted in aerosol transport into this region being mainly in the marine boundary layer (MBL), although lower free troposphere transport was possible on the western sides of Sumatra and Borneo. At the hourly time scale, particle concentrations were observed to be modulated by integer factors through convection and associated cold pools. Geostationary satellite observations suggest that convection often takes the form of squall lines, which are bowed up to 500 km across the monsoonal flow and 50 km wide. These squall lines, initiated by cold pools from large thunderstorms and likely sustained by a veering vertical wind shear and aforementioned mid-troposphere dry layers, propagated over 1500 km across the entirety of the SCS/ES, effectively cutting large swaths of MBL aerosol particles out of the region. Our conclusion is that while large-scale flow patterns are very important in modulating convection, and hence in allowing long-range transport of smoke and pollution, more short-lived phenomena can modulate cloud condensation nuclei (CCN) concentrations in the region, resulting in pockets of clean and polluted MBL air. This will no doubt complicate large scale comparisons of aerosol–cloud interaction.

DOI： https://doi.org/10.5194/acp-15-1745-2015

Language：English   Publishing type：Research paper (scientific journal)  

Ground-based observations have insufficient spatial coverage to assess long-term human exposure to fine particulate matter (PM2.5) at the global scale. Satellite remote sensing offers a promising approach to provide information on both short- and long-term exposure to PM2.5 at local-to-global scales, but there are limitations and outstanding questions about the accuracy and precision with which ground-level aerosol mass concentrations can be inferred from satellite remote sensing alone. A key source of uncertainty is the global distribution of the relationship between annual average PM2.5 and discontinuous satellite observations of columnar aerosol optical depth (AOD). We have initiated a global network of ground-level monitoring stations designed to evaluate and enhance satellite remote sensing estimates for application in health-effects research and risk assessment. This Surface PARTiculate mAtter Network (SPARTAN) includes a global federation of ground-level monitors of hourly PM2.5 situated primarily in highly populated regions and collocated with existing ground-based sun photometers that measure AOD. The instruments, a three-wavelength nephelometer and impaction filter sampler for both PM2.5 and PM10, are highly autonomous. Hourly PM2.5 concentrations are inferred from the combination of weighed filters and nephelometer data. Data from existing networks were used to develop and evaluate network sampling characteristics. SPARTAN filters are analyzed for mass, black carbon, water-soluble ions, and metals. These measurements provide, in a variety of regions around the world, the key data required to evaluate and enhance satellite-based PM2.5 estimates used for assessing the health effects of aerosols. Mean PM2.5 concentrations across sites vary by more than 1 order of magnitude. Our initial measurements indicate that the ratio of AOD to ground-level PM2.5 is driven temporally and spatially by the vertical profile in aerosol scattering. Spatially this ratio is also strongly influenced by the mass scattering efficiency.

DOI： https://doi.org/10.5194/amt-8-505-2015

Language：English   Publishing type：Research paper (scientific journal)  

Southeast Asia (SEA) hosts one of the most complex aerosol systems in the world, with convoluted meteorological scales, sharp geographic and socioeconomic features, high biological productivity, mixtures of a wide range of atmospheric pollutants, and likely a significant susceptibility to global climate change. This physical complexity of SEA is coupled with one of the world's most challenging environments for both in situ and remote sensing observation. The 7-Southeast Asian Studies (7SEAS) program was formed to facilitate interdisciplinary research into the integrated SEA aerosol environment via grass roots style collaboration. In support of the early 7SEAS program and the affiliated Southeast Asia Composition, Cloud, Climate Coupling Regional Study (SEAC4RS), this review was created to outline the network of connections linking aerosol particles in SEA with meteorology, climate and the total earth system. In this review, we focus on and repeatedly link back to our primary data source: satellite aerosol remote sensing and associated observability issues. We begin with a brief rationale for the program, outlining key aerosol impacts and, comparing their magnitudes to the relative uncertainty of observations. We then discuss aspects of SEA's physical, socio-economic and biological geography relevant to meteorology and observability issues associated with clouds and precipitation. We show that not only does SEA pose significant observability challenges for aerosol particles, but for clouds and precipitation as well. With the fundamentals of the environment outlined, we explore SEA's most studied aerosol issue: biomass burning. We summarize research on bulk aerosol properties for SEA, including a short synopsis of recent AERONET observations. We describe long range transport patterns. Finally, considerable attention is paid to satellite aerosol observability issues, with a face value comparison of common aerosol products in the region including passive and active aerosol products as well as fluxes. We show that satellite data products diverge greatly due to a host of known artifacts. These artifacts have important implications for how research is conducted, and care must be taken when using satellite products to study aerosol problems. The paper ends with a discussion of how the community can approach this complex and important environment.

DOI： https://doi.org/10.1016/j.atmosres.2012.06.005

Language：English   Publishing type：Research paper (scientific journal)  

Continuous data of aerosol optical thickness monitored using differential optical absorption spectroscopy (DOAS) are correlated with the concentration of ground-measured suspended particulate matter (SPM). A high correlation is found between the DOAS and the ground SPM data, making it possible to calculate the mass extinction efficiency of the aerosols in the atmosphere. It is found that the value of mean mass extinction efficiency (MEE) varies over a range of 2.6–13.7 m2 g−1, with smaller and larger values occurring for size distributions dominated by coarse and fine particles, respectively.

DOI： https://doi.org/10.1007/s00376-006-0461-z

Language：English   Publishing type：Research paper (scientific journal)  

With the method of differential optical absorption spectroscopy (DOAS), average concentrations of aerosol particles along light path were measured with a flashlight source in Chiba area during the period of one month. The optical thickness at 550 nm is compared with the concentration of ground-measured suspended particulate matter (SPM). Good correlations are found between the DOAS and SPM data, leading to the determination of the aerosol mass extinction efficiency (MEE) to be possible in the lower troposphere. The average MEE value is about 7.6m2.g−1 and the parameter exhibits a good correlation with the particle size as determined from the wavelength dependence of the DOAS signal intensity.

DOI： https://doi.org/10.1088/1009-1963/14/11/037

Language：English   Publishing type：Research paper (scientific journal)  

Continuous data of the atmosphere monitored using a portable automated lidar are correlated with the concentration of ground-measured suspended particulate matter (SPM). When the boundary layer is well mixed, a high correlation is found between the lidar and the ground SPM data, making it possible to calculate the mass extinction efficiency of the aerosols in the atmosphere. It is found that within the ground layer, the value of mean mass extinction efficiency changes in a range of 4–12 m²g^-1, with smaller and larger values occurring for size distributions dominated by coarse and fine particles, respectively.

DOI： https://doi.org/10.1016/j.jaerosci.2004.10.007

Language：English   Publishing type：Research paper (scientific journal)  

A compact, continuously operated lidar system has been developed and applied for unattended, continuous monitoring of troposphere. We demonstrate the effectiveness of the automatic procedure that routinely optimizes the lidar alignment in a definite interval. On the basis of the data taken from December 2002 to June 2003, oscillatory behavior of the aerosol layer height, vertical motion of the aerosol layer, and speed of raindrops are discussed. A good correlation is found between the lidar signal backscattered inside the boundary layer and the data of suspended particulate matter simultaneously measured at the ground level.

DOI： https://doi.org/10.1016/j.atmosenv.2004.02.060

Event date： 2024.6

Language：English   Presentation type：Poster presentation  

Venue：German Aerospace Center   Country：Germany  

Event date： 2024.6

Language：English   Presentation type：Poster presentation  

Venue：German Aerospace Center, Landshut,   Country：Germany  

Other Link： https://ilrc-clrc-2024.welcome-manager.de/

Event date： 2024.2

Language：English   Presentation type：Oral presentation (general)  

Venue：Rome   Country：Italy  

Changes in environmental conditions can be evaluated by detecting the conditions in indicator plants. Indicator plants are sensitive to specific environmental stresses. This research focused on white clover as an indicator plant for ozone. To analyze the effects of weaker stresses, compact OCT (Optical coherence tomography) for plants was developed, which allows for non-invasive and non-contact cross-sectional imaging of white clover (Trifolium repens) leaves exposed to ozone gas. OCT image changes on each level of ozone damage were evaluated using parameters such as the OCT signal level of the leaf palisade layer, the thickness of the leaf palisade layer, and texture analysis using GLCM (Gray-Level Co-occurrence Matrix). Measurements of leaves grown in our laboratory showed increased palisade tissue signal, thicker palisade tissue, a smaller distribution of palisade layer thickness, increased OCT image contrast, and decreased OCT image homogeneity.

Event date： 2023.12

Language：English  

Venue：Moscone Center, San Francisco   Country：United States  

The near-ground atmosphere was continuously monitored using a Vaisala PWD52 visibility meter at Chiba University from April 2017 to March 2018. Visibility data, collected at 1-minute intervals, were utilized to calculate the extinction coefficient employing the Koschmieder equation at a wavelength of 550 nm. Throughout the year, daily and seasonal changes in the extinction coefficient were observed. Extinction coefficients and the relative humidity (RH) data obtained from a Davis Instruments Vantage Pro 2 weather monitor are analyzed. During the year-long operation, it was found that the extinction coefficients in the spring, fall, and winter months were approximately twice as high (~2.5×10-4 m-1) in the 80% to 90% RH range compared to the summer months. This observation suggests that the dominant aerosols demonstrated enhanced activity during the spring, fall and winter, where they exhibited increased growth under specific RH conditions. This phenomenon was attributed to prevailing wind directions originating from the land (east to north), transporting organics and ammonium nitrate into the fine mode region during the spring, fall, and winter months (Fukagawa et al., 2005). In contrast, during summer, when the prevailing winds emanated from the Tokyo Bay area (south), the fine mode region was dominated by ammonium sulfate, which exhibited a lower growth factor than ammonium nitrate.
Based on these results, the monthly extinction enhancement factor, denoted as f(RH), was computed by comparing the extinction coefficient at a given RH to that at a dry RH. The findings indicated that f(RH) values in the 80% to 90% RH range during the spring, fall, and winter months were approximately 2.2 times higher than those observed in summer. Moreover, at nearly 100% RH, f(RH) values reached up to 38, indicating a significant impact of relative humidity on aerosol extinction coefficients.

This study provides valuable insights into the seasonal variability of aerosol extinction coefficients and their dependence on relative humidity, contributing to a better understanding of aerosol behavior in the near-ground atmosphere.

Other Link： https://agu.confex.com/agu/fm23/meetingapp.cgi/Paper/1379430

Event date： 2023.12

Language：English  

Venue：Moscone Center, San Francisco   Country：United States  

Nighttime cloud observations have been conducted using cost-effective, commercially available ground-based cameras in a collaborative network spanning nearly three years. The primary objectives of this network are to: 1) continuously acquire nighttime cloud images, 2) analyze and quantify local cloud cover (CC) and its temporal changes, 3) correlate CC with satellite observations, 4) quantify the effects of cloud on longwave radiative forcing in the atmosphere, and 5) quantify CC changes at each latitude. The network currently operates five camera systems at distinct locations: Chiba University (Japan), National Central University (Taiwan), National Institute of Technology, Toyama College (Japan), Research Institute for Sustainable Humanosphere, Kyoto University (Japan), University of Guam (USA), and a new site at Kyushu University (Japan) in early August 2023. Each camera system comprises two cameras, one equipped with a near-infrared (NIR)-cut filter and the other without. These cameras operate simultaneously, capturing nighttime sky images at 5-minute intervals from 16:30 local time until 07:00 the following day.
Cloud detection is achieved by applying a threshold value to the pixels based on numerous clear and cloudy images, cross-referenced with satellite data (Himawari 8). Current observations indicate that a universal standard threshold pixel value cannot be applied if the exposure time is fixed at 5 seconds across all sites. Environmental conditions unique to each location influence cloud detection efficiency. Notably, nighttime clouds are readily detected in urban areas with city lights, exemplified by Chiba University, National Central University, and Guam. In such cases, with a 5-second exposure time, a threshold pixel value of 17, specific to this camera, can effectively differentiate clear from cloudy pixels for images captured with the NIR-cut filter. For images from the camera without the NIR-cut filter, threshold values of 71 and 115 can distinguish clear from thin clouds and thin clouds from thick clouds, respectively. However, sites with limited city lights require a longer acquisition time (15 to 30 seconds) to achieve similar threshold pixel values. These findings enable the computation, analysis, and comparison of CC data from each site with other remote sensing instruments.

Event date： 2023.11

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Comparing cloud cover (CC) products from different satellites with the same ground-based CC dataset provides information on the similarities or differences of values among satellite products. For this reason, 42-month CC products from Moderate Resolution Imaging Spectrometer’s (MODIS) Collection 6.1 daily cloud cover products (MOD06_L2, MYD06_L2, MOD08_D3, and MYD08_D3) and Himawari-8 are compared with the ground-based camera datasets. The comparison shows that CC from MODIS differs from ground measurement CC by as much as 57% over Chiba, Japan, when low CC is observed by the camera. This indicates MODIS’s ability to capture high-level clouds that are not effectively seen from the ground. When the camera detects high CC, an indication of the presence of low-level clouds, CC from MODIS is relatively higher than the CC from the camera. In the case of Himawari-8 data, when the camera observes low CC, this difference is around 0.7%. This result indicates that high-level clouds are not effectively observed, but the Himawari-8 data correlates well with camera observations. When the camera observes high CC, Himawari-8-derived CC is lower by around 10% than CC from the camera. These results show the potential of continuous observations of nighttime clouds using the camera to provide a dataset that can be used for intercomparison among nighttime satellite CC products.

Event date： 2023.9

Language：English  

Venue：Amsterdam   Country：Netherlands  

Event date： 2023.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Amsterdam   Country：Netherlands  

Event date： 2023.2

Language：English  

Venue：Lisbon   Country：Portugal  

Event date： 2022.12

Language：English  

Venue：McCormick Place, Chicago   Country：United States  

Event date： 2022.6 - 2022.7

Language：English  

Venue：Big Sky, Montana   Country：United States  

Local transport of radioactive dust can put the environment and nearby people at risk. A plan to continuously monitor radioactive dust using synchronized measurements from horizontally pointing lidar and other instruments (e.g., weather monitor, dust sampler, particle counters) in uninhabited areas in Fukushima, Japan, is being considered. Data from continuous observations near a radioactive area can elucidate the effects of weather on the optical properties of aerosols. They can also provide information on how radioactive dust is transported when used in transport models. A pre-deployment continuous observations using a horizontal lidar and weather sensors were made on August and 21 December 2021. Results show that extinction coefficients are relatively higher (~4 × 10−3 m−1) in August compared to the values observed in December (~2.5 × 10−3 m−1). Diurnal effects on aerosol optical properties are highly observed in the depolarization ratio values. High depolarization ratios are observed during the daytime. A higher depolarization ratio (~0.12) is also measured in winter, and this can be attributed to changes in aerosol type due to changes in wind direction.

Other Link： https://link.springer.com/search?query=lagrosas&facet-eisbn=978-3-031-37818-8&facet-content-type=Chapter

Event date： 2022.6 - 2022.7

Language：English  

Venue：Big Sky, Montana   Country：United States  

In this work, we propose a low coherence Doppler lidar (LCDL) to measure dust flow at near-surface atmosphere. To get dust flow information at near-surface atmosphere, it is necessary to measure it with high spatial and high temporal resolutions. Low coherence light source of Δλ = 0.5 pm can satisfy this high-resolution criterion of <1 m. In addition, by shortening the integration time to <5 ms, high-speed measurement can be performed on the small spatiotemporal scale of the lower atmosphere. A dust experiment is conducted to evaluate LCDL performance by shaking dust (wheat flour) off into a wind tunnel. The measurement speed of LCDL is compared with the speed of anemometer. At speeds from 0 to 5 m/s, they show good linear agreement. The distribution of dust flow is obtained with the Doppler shift frequency width of >1 MHz. We simulated the experiment condition to calculate it with a viscous resistance. The waveform obtained by the calculation has the same Doppler shift frequency width of >1 MHz with the experiment.

Other Link： https://link.springer.com/search?query=lagrosas&facet-eisbn=978-3-031-37818-8&facet-content-type=Chapter

Event date： 2022.6 - 2022.7

Language：English  

Venue：Big Sky, Montana   Country：United States  

Interaction between the sea surface and the lower atmosphere is important. Especially in the shore, such interaction becomes more fruitful but complex because the sea wave dynamics and wind will mix in the interaction. It is worthwhile to monitor such interaction for geophysics, marine science, and technologies for revetment and boat maneuver. In this study, we focused on the above interaction monitoring and its visualization. The LED-based mini-lidar is developed to visualize the interaction. To follow the high temporal and spatial dynamics in the shore, the LED lidar system has the high resolutions’ performance of 0.2 s summation time and 0.15 m spatial intervals. We have been continued the field experiments in an inland sea (Tokyo bay) and oceans (Pacific ocean). The wave motions are confessedly different linking to the sea floor orientation, tide current, and weather. The LED lidar system set to the near horizontal direction at shallow angle. The interactions between the sea wave and the wind have been captured under the several weather conditions and observation locations. By the synchronized measurement with weather sensor, the sea wave dynamics are discussed with the wind profile.

Other Link： https://link.springer.com/search?query=lagrosas&facet-eisbn=978-3-031-37818-8&facet-content-type=Chapter

Event date： 2022.6 - 2022.7

Language：English  

Venue：Big Sky, Montana   Country：United States  

A multiwavelength lidar system with a light-emitting diode (LED)-based light source is designed and developed to continuously monitor near-surface atmosphere at nighttime. The LED light source does not require any heat dissipation system and can emit optical power for long periods with constant output. The LED light sources with wavelengths of 365, 450, 525, and 630 nm are used as lidar transmitters to detect hard target and atmospheric echoes. The pulse circuit for realizing the pulsed oscillation of the LED lights is applied by the avalanche breakdown of the transistor. These LED pulsed lights can be synchronized by serially concatenated to the circuit. The LED has a pulse width of around 17 ns, repetition frequency of over 250 kHz, and each peak power of up to 2 W. With these LED transmitter characteristics, the lidar system accomplishes monitoring the atmosphere’s rapid activities in the near-range measurement. Initial near-surface observation results from 365 and 450 nm show that atmospheric echoes can be monitored in the range of 0–300 m at an accumulation time of a few tens of seconds at nighttime. Analysis of the backscattering light intensity with multiwavelengths from this LED lidar system produces a real-time extinction coefficient near the surface. This report discusses the design and practical test of the multiwavelength LED lidar.

Other Link： https://link.springer.com/search?query=lagrosas&facet-eisbn=978-3-031-37818-8&facet-content-type=Chapter

Event date： 2022.2

Language：Japanese   Presentation type：Poster presentation  

Venue：online   Country：Japan  

Event date： 2021.12

Language：English  

Venue：Hybrid Conference, New Orleans   Country：United States  

Event date： 2021.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Hybrid Conference, New Orleans   Country：United States  

Event date： 2021.11

Language：English  

Venue：Online   Country：Other  

Event date： 2021.11

Language：English  

Country：Japan  

Event date： 2021.11

Language：English  

Venue：Online   Country：Other  

Event date： 2021.11

Language：English  

Venue：Online   Country：Other  

Event date： 2021.11

Language：English  

Venue：Online   Country：Other  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：online   Country：Japan  

Other Link： https://laser-sensing.jp/lss39/lss39_program.pdf

Event date： 2021.3

Language：Japanese  

Venue：Online   Country：Japan  

Event date： 2020.12

Language：English  

Venue：Online   Country：Other  

Event date： 2019.12

Language：English  

Venue：Moscone Center, San Francisco   Country：United States  

Event date： 2019.11

Language：English  

Venue：Gifu Chamber of Commerce and Industry, Gifu   Country：Japan  

Type：Academic society, research group, etc.